JPH054133B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a catalyst for removing carbonyl sulfide (COS) contained in various gases by hydrolysis.

[Conventional technology and its problems]

By hydrolyzing the COS contained in the gas in the presence of a solid catalyst such as alumina or silica and converting it into H ₂ S, the H ₂ S is removed using a wet method.
It is already known to remove COS. It is also clear that this reaction proceeds on the acid or base sites on the catalyst, and it is natural that the catalyst activity can be influenced by quantitatively controlling these acid or base sites. You can look forward to it.

For example, JOURNAL OF CATALYSIS 32
270 (1974), the use of _Al2O3 catalysts to hydrolyze COS was also reported in JOURNAL _OF
CATALYSIS 35 218~ (1974) describes that the activity was significantly improved by adding NaOH to Chromosorb-A, which has silica as its main component.

However, these reactions are generally carried out at high temperatures of 200°C or higher, and the above report also states that
The reaction takes place at temperatures around 230°C or higher.

Although it is generally desired that such reactions be carried out at low temperatures, it is not yet known that COS can be hydrolyzed in the presence of a catalyst at a low temperature of 200°C or lower, particularly 150°C or lower.

It is also possible to remove COS from the gas by hydrogenating COS, but this hydrogenation reaction requires a high reaction temperature of 300°C or higher, and the CO concentration in the gas to be treated is low. If it is high, it is not favorable from the viewpoint of chemical equilibrium.

Therefore, in this sense as well, a COS hydrolysis process that can be processed at a relatively low temperature is preferable.

[Purpose of the invention]

An object of the present invention is to provide a catalyst that can effectively hydrolyze COS even at low temperatures.

[Structure of the invention]

The present invention consists of alumina and barium oxide.
It is a catalyst for COS hydrolysis.

The present inventors were conducting various research on COS hydrolysis catalysts made of alumina, and found that by adding Ba to alumina catalysts, they could be improved in the low temperature range.
It has been found that COS hydrolysis activity can be improved.

The catalytic activity of ordinary Al ₂ O ₃ catalysts decreases significantly below 150°C, and one of the reasons for this is that H ₂ O
The reason why the initial activity improves in the low temperature range by adding Ba to Al ₂ O ₃ is due to the affinity between Al ₂ O ₃ and H ₂ O. It is understood that Ba contributes to the decrease in sex.

Further, by adding Ba to Al ₂ O ₃ , deterioration of the catalyst can be drastically reduced. The reason for this is complex and cannot be clearly explained, but at low temperatures
Al ₂ O ₃ causes a solid phase reaction with H ₂ O, forming a part of hydrated compounds such as boehmite, and this causes changes in the geometric structure of the catalyst surface, or changes in acid sites and basic sites. It is thought that the activity decreases due to chemical and electronic qualitative changes. This can be supported by the fact that the addition of Ba clearly alleviates the deterioration of the catalyst and also that the formation of boehmite in alumina is reduced.

The alumina used in the present invention is γ,
Alumina having any structure such as χ, κ, θ, or α may be used, but γ alumina is preferable.

A method for adding Ba to alumina is to impregnate alumina with an aqueous solution of a barium compound such as barium nitrate, barium hydroxide, or barium acetate, and then at a temperature higher than the decomposition temperature of the above compound, for example, at a temperature higher than 250°C. In addition, it is the alteration or sintering (surface area reduction) temperature of alumina.
It is sufficient to perform firing at a temperature within a range of 800°C or less while sufficiently circulating air.

The amount of barium compound added to alumina is
An amount within the range of 0.1 to 10 Ba atoms per 100 atoms is preferable; an amount of less than 0.1 will not produce a sufficient effect, and an amount of more than 10 will be meaningless.

In the catalyst of the present invention, Ba is thought to exist in the form of barium oxide or barium aluminate (complex oxide with alumina).

Catalysts are generally used in the form of spheres, pellets, raschich rings, etc., but honeycomb shapes can also be used from the viewpoint of pressure loss and dust countermeasures.

When removing COS from gas using the catalyst of the present invention, for example, coal gasification gas or heavy oil gasification gas (usually 10ppm in these gases)
Contains ~1000ppm COS), ~90℃
Ba at a temperature within the range of 200℃, under a pressure of normal pressure to 20Kg/ ^cm2 , and in the presence of 1 to 30% steam.
The gas may be passed over a catalyst containing gas at a gas hourly space velocity of 900 to 30,000 h ^- .

By this treatment, the ion content of COS in the raw material gas is converted to H ₂ S, so in many cases, this H ₂ S can be easily removed by a wet absorption method.

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Comparative Example 1 Catalyst A was obtained by calcining an alumina catalyst molded into a spherical shape of 4 mm to 10 mm at 600° C. for 5 hours in an electric furnace under air circulation.

Example 1 100g of the alumina catalyst used in Comparative Example 1 was added to 500c.c.
70 c.c. of a 0.28 mol/barium nitrate aqueous solution was dropped onto the alumina at room temperature to impregnate it. After drying in a conventional manner, the mixture was placed in an electric furnace and calcined at 600° C. for 5 hours under air circulation to obtain catalyst B. The Ba/Al atomic ratio was 1/100.

Examples 2 to 4 Instead of barium nitrate aqueous solution in Example 1
0.035mol/, 0.071mol/ and 0.141mol/
Using barium nitrate aqueous solution, the atomic ratio of Ba/Al was 0.125/100 and 0.25/
100 and 0.5/100 catalysts C, D and E were obtained.

Examples 5 to 6 Samples with Ba/Al atomic ratios of 2/100 and 3/100 were prepared in the same manner as in Example 1, except that 70 c.c. of 0.28 mol/barium nitrate aqueous solution was impregnated twice and three times. Catalysts F and G were obtained.

Example 7 The same procedure as Example 1 was carried out except that 70 c.c. of 0.35 mol/barium nitrate aqueous solution was impregnated four times.
A catalyst H having a Ba/Al atomic ratio of 5/100 was obtained.

Example 8 The same procedure as Example 1 was carried out except that 70 c.c. each of 0.40 mol/barium nitrate aqueous solution was impregnated seven times.
Catalyst I with a Ba/Al atomic ratio of 10/100 was obtained.

Example 9 Catalyst J having a Ba/Al atomic ratio of 1/100 was obtained in the same manner as in Example 1 except that a 0.28 mol/barium hydroxide aqueous solution was used.

Example 10 A catalyst K having a Ba/Al atomic ratio of 1/100 was obtained in the same manner as in Example 1 except that a 0.28 mol/aqueous barium acetate solution was used.

Example 11 500g of alumina catalyst powder used in Comparative Example 1
into a stirring kneader, add a small amount of pure water,
500 c.c. containing 25.6 g barium nitrate with stirring.
An aqueous solution of was added in small portions. The resulting paste was heated while kneading to adjust the water content to about 20% by weight, molded into pellets using a screw-type extruder, dried, and then calcined at 600°C for 5 hours to form catalyst L.
I got it.

Usage Example 1 The initial COS hydrolysis activities of catalysts A to E and G obtained in Comparative Example 1 and Examples 1 to 4 and 6 were measured using a conventional fixed bed flow reactor.

A Pyrex reaction tube with a length of 55 cm and an inner diameter of 20 mm was filled with 10 c.c. of catalyst, and the reaction conditions were 100°C to 190°C at normal pressure.
The temperature was SV8000h ^-1 . Furthermore, as a gas
A gas consisting of balanced N ₂ with a COS concentration of 200 ppm and a H ₂ O concentration of 30% was used. The results are shown in Figure 1.

As can be seen from Figure 1, when the reaction temperature is below 150°C, the activity of catalyst A decreases considerably, but
In the catalyst of the present invention in which the phosphor was added, the decrease was clearly reduced.

Application Example 2 Long-term use of catalysts A, B, J, K and L obtained in Comparative Example 1 and Examples 1, 9 to 11
The COS hydrolysis reaction was tested. It was carried out in the same manner as in Use Example 1 except that the reaction temperature was 130°C.

The results are shown in Figure 2.

From FIG. 2, it can be seen that catalysts B, J, K, and L of the present invention containing barium exhibit significantly less catalyst deterioration over time than catalyst A that does not contain Ba.

Usage Example 3 Catalysts A, B, F, H, and I obtained in Comparative Example 1 and Examples 1, 5, 7, and 8 were treated with air containing water vapor to examine changes in alumina over time.
The experiment was conducted at 130° C. under normal pressure in an atmosphere of 30% H ₂ O concentration and 70% air.

The results are shown in Figure 3.

The amount of boehmite produced increases with treatment time in Catalyst A without barium, but clearly decreases in the catalyst of the present invention with barium added.

This suggests that one of the causes of catalyst deterioration in the COS hydrolysis reaction is alteration of alumina.

[Brief explanation of drawings]

Figures 1 and 2 show that the catalyst of the present invention is superior to alumina catalysts in terms of initial activity and deterioration of activity, and Figure 3 shows that the catalyst of the present invention is superior to alumina catalysts in terms of water vapor. FIG. 3 is a diagram showing that the boehmite production rate due to processing is low.

Claims (1)

[Scope of Claims] 1. A catalyst for hydrolysis of carbonyl sulfide comprising alumina and barium oxide. 2. The catalyst according to claim 1, comprising barium in an atomic ratio of 0.1 to 10 to Al100 in alumina.